1. Field of the Invention
The present invention relates to a tubular lining material for pipe lines which comprises a tubular textile jacket overlaid superficially on the external surface thereof with air-impervious plural coatings of flexible synthetic resins having strongly been bonded to the textile jacket and to a method and apparatus for manufacturing same. More particularly, the present invention relates to a tubular lining material for pipe lines, especially underground pipe lines already constructed, which comprises a tubular textile jacket made of warps and a weft knitted or woven in a tubular form superficially overlaid with air-impervious plural coatings of flexible synthetic resins having strongly been bonded to the textile jacket and to a method and apparatus for manufacturing same wherein a combination of synthetic resins is suitably selected and a specific device is made for simultaneous extrusion and bonding of plural synthetic resins superficially but strong onto the external surface of the tubular textile jacket.
2. Description of the Prior Art
In the past, a tubular textile jacket which is normally a fabric having been woven with warps and a weft in a tubular form was coated on the external surface thereof with a latex of natural rubber or a synthetic resin and then turned inside out in the open air to manufacture a fire hose. In a typical method for manufacturing such fire hose comprised a series of continuous steps of dipping a tubular textile jacket reeled off from a supply reel into a bath of an emulsion of a latex or a synthetic resin, drying the tubular textile jacket while being kept in an inflated state to form a coating of a latex of natural rubber of a synthetic resin on the external surface of the jacket and thereafter turning the tubular textile jacket inside out in the open air by applying a pressurized fluid to the interior space of the jacket to form a fire hose having a resinous coating on the inner surface thereof. The most advantageous method of this type, for example, a method disclosed in U.S. Pat. No. 4,020,790 is still utilized for the manufacture of fire hose.
In recent years, such tubular textile jacket with a coating of a synthetic resin on the external surface thereof has been utilized as a lining material for pipe lines, especially underground pipe lines such as gas conduits, city water pipe lines, petroleum pipe lines, sewage pipes made of concrete or porcelain and pipe lines enclosing power transmission wires or telecommunication cables. In case of such underground pipe lines, their superannuation or damage often causes dangerous leakage of combustible fluids or electricity and unexpected burst of water, thus resulting in accidents and traffic disturbance. Only one effective countermeasure taken in the past to prevent such troubles was to dig up the superannuated or damaged pipe lines over the length in the order of several ten or hundred meters for replacing them with new ones. During this pipeexchange work, people encounter a great deal of trouble since supply of gas or city water or fuels is discontinued and even traffic is limited where the pipe lines are buried below the public roads. In such a case, enormous labor and cost are required for the pipeexchange work in addition to the difficulty in the work itself. Thus, development of such a pipe-lining material and a method for applying it to underground pipe lines attracts commercial interest because there no longer is the necessity of digging up the pipe lines already constructed. A method for lining pipe lines with such resin-coated tubular textile jacket as a tubular lining material has been hitherto improved several times. A typical improvement now advantageously utilized is disclosed. For example, U.S. Pat. No. 4,334,943 discloses passing such a tubular lining material through a pipe line and evaginating it within the pipe line under fluid pressure while bonding the evaginated tubular lining material onto the inner surface of the pipe line by the aid of a binder with or without using a leading rope-like material. Said material has previously been passed through the tubular lining material beyond its full length and is drawn from the opposite end of the pipe line. It has been found, however, that the tubular textile jacket with a coating of a synthetic resin on the external surface thereof which can be manufactured according to a method as disclosed in U.S. Pat. No. 4,020,790 is not suitable as a tubular lining material for the above pipelining method. According to the method described in this patent, a tubular textile jacket is dipped in a bath of an emulsion of a latex or a synthetic resin whereby the emulsion is penetrated deeply into the interstices of the fabric structure and is solidified in the subsequent drying step to harden the textile jacket. It is difficult to evaginate the hardened tubular textile jacket within a narrow space, i.e. a pipe line under normal fluid pressure. If the fluid pressure is elevated to strengthen the force necessary for evagination, the tubular lining material may often be damaged or stress may be formed therein under such high pressure.
With the improvements made in the pip-lining methods, some improvements have also been made in tubular lining materials themselves. Thus, a tubular lining material used in the pipelining method described in U.S. Pat. NO. 4,334,943 is a textile jacket woven in a tubular form with warps and a weft made of polyester yarns and having on the external surface thereof a coating of a polyester resin. The synthetic resin used in this tubular lining material is generally a thermoplastic polyester elastic resin such as Pelprene (Toyobo, Japan) or Hytrel (DuPont, U.S.A.) while the binder is preferably a commercially available thermocurable epoxy resin. As the polyester elastic resin possesses both strength and flexibility, this tubular lining material can provide a strong and satisfactory inner backing for the pipe lines. However, a problem exists in this polyester resin with respect to cohesion to the epoxy binder and to the textile jacket made of polyester yarns.
In general, what is needed for the tubular lining material is that it must be impregnated with a sufficient amount of a binder before the lining treatment but must easily be evaginated under a relatively weak fluid pressure so that the lining material can be bonded, after evagination, strongly onto the inner surface of a pipe line to form an integrally solidified reinforced textile pipe line within the pipe line as if the reinforced textile jacket were regarded as a second pipe line formed within the pipe line treated. In particular, the following properties are requested for the coating of a synthetic resin:
(1) To be flexible (The coating should be flexible for maintaining flexibility of the lining material. The hardness or the coating is preferably soft enough to assure evagination of the tubular lining material or less than 95 in terms of Shore A hardness.) PA1 (2) To have a sufficient tensile strength PA1 (3) To possess stretchability PA1 (4) To be lower in frictional resistance between the coatings and to be better in anti-abrasion resistance PA1 (5) To be excellent in the resisting properties against chemicals, solvents, water and fungi PA1 (6) To be heat-resistant PA1 (7) Not to degrade against a binder to be used PA1 (8) To show good cohesion between the coating and the binder after curing of the binder PA1 (9) To be easily moldable (As an extrusion molding method is usually utilized to form a coating of a synthetic resin on the external surface of the tubular textile jacket, the synthetic resin is required to have good moldability.) PA1 (10) To show good adhesion to the tubular textile jacket by extrusion molding.
As the thermoplastic polyester elastic resin cannot be applied onto the external surface of a tubular textile jacket according to the so-called dipping method wherein the jacket is dipped in a bath of an emulsion or solution of the resin and then dried, tubular lining materials employed in the current pipelining methods as disclosed in U.S. Pat. Nos. 4,334,943, 4,368,091, 4,350,548 and 4,427,480 are manufactured by applying the elastic resin onto the tubular textile jacket according to an extrusion molding method wherein the resin is extruded while hot onto the external surface of the tubular textile jacket in inflated state. The thermoplastic polyester elastic resin such as Pelprene or Hytrel substantially satisfies the above requirements (1)-(7) and (9) and is generally preferred as a coating on the tubular textile jacket. It may not be difficult to improve the adhesion of the polyester resin to the tubular textile jacket. When the resin is extruded under high pressure onto the surface of the textile jacket on extrusion molding, the resin is forced to penetrate deeply in interstices of the fabric structure of the textile jacket whereby the resin is strongly bonded to the textile jacket by the so-called anchoring action. However, this device bears on the other hand such a disadvantage that the resin deeply intruded into the textile jacket is solidified to damage flexibility of the lining material and gives no sufficient space in the jacket for absorbing a necessary amount of a binder. The tubular lining material having poor flexibility cannot easily be evaginated within a pipe line unless the fluid pressure be elevated, and cannot be bonded firmly onto the inner surface of the pipe line when impregnated with an insufficient amount of the binder. At present, a new type synthetic resin of excellent coating characteristics has not yet been developed which can be substituted for the thermoplastic polyester elastic resin now suitably used as a resinous coating on the tubular textile jacket made of polyester yarns.
Under these circumstances, there is a technical subject for improving adhesion of the thermoplastic polyester elastic resin to the textile jacket and also a great demand for developing a new tubular lining material having on the external surface thereof a coating of a synthetic resin which satisfies all of the above requirements (1)-(10) and can strongly be bonded to the textile jacket without any sacrifice of its flexibility and complete adhesion of the lining material to the inner surface of the pipe line.